Control apparatus



1950 F. T. DEZIEL 2,955,650

CONTROL APPARATUS Filed July 24, 1958 .0 46 J 1 5 LIMIT g comRo 55 a LINE INVENTOR. FRED T. DEZIEL E ma a v ATTORNEY 2,955,650 a H CONTROL APPARATUS Fred T. Deziel, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, 7 Minn., a corporation of Delaware Filed July 24, 1958, Ser. No. 750,631 I 9 Claims. or 158-128) The present invention is concerned with an improved control apparatus and more particularly with an improved burner control apparatus utilizing an electronic flame detector in combination with a main burner control relay wherein the energizing circuit for the main burner control'relay is associated with the cathode heater of an electron discharge device such that in the event the electronic flame detector becomes inoperative due to an open heater circuit, the main burner control relay is deenergized to thereby de-energize the fuel burner unit being controlled.

The primary consideration of a fuel'burner control apparatus is to provide safe and reliable operation of an associated fuel burner unit. This is to be accomplished with a minimum of cost and yet safety must not be sacrificed for the cost consideration. The use of electronic flame detectors provides a safe and fast sensing of the presence or absence of flame at the fuel burner unit and has found wide acceptance, particularly with fuel burner consuming a large quantity of fuel per hour. I

The prior art teaches the advantage of providing interlocking circuit means between a flame relay and a main burner control relay such that the main burner control relay may not be initially energized unless the flame relay is in a condition indicating the absence of flame at the fuel burner unit. Such a construction insures that the main burner control relay will not be energized if the electronic flame detector has failed such that the flame relay falsely indicates the presence of flame in the fuel burner unit whereas the flame is in fact not present.

The present invention utilizes this feature as well as the further features whereby theelectronic flame detector itself is not initiallyrendered operative-unless theburner control relay is in its d e-energized condition, that is a condition indicating that there is no need for operating the fuel burner unit. The present invention utilizes an electronic flame detector in whichthe flame relay is energized in the absence of flame at the fuel burnerunit such that upon initial energizationof the control apparatus, the flame relay is rendered energized only if the main burner control relay is in its de-energized condition.

in the art upon' reference to the following specification;

claims, and drawing, of which the single figure is a schematic representation of the present invention. V Referring to the single figure, the apparatus disclose therein can be divided into three basic portions. The first" of these portions is designated generally by the reference numeral 10 and is a control network which controls a main fuel burner control relay 11 having a winding 12 and switches 13, 14, and 15. The main control relay 11. is shown in the de-energized condition wherein the switches 13 and 15 are open and the switch 14 is lcloedf The control network 10 includes as an element thereofa safety lock-out means 16 in the form of a' bimetal op erated switch. The safety lock-out means includes the normally closed switch 17, an electrically energizable heater 18 and a bimetal operator 19. The device 16 is of a conventional construction and operates such that after a time period of energization of heater 18, the

' performing a safety lock-out function which de-energizes The flame relay whenenergized controls switch means in electronic flame detector-insensitive of the absence of l flame at the fuel burner unit, and therefore if the flame should fail, the control apparatus doesln ot sense this flame failure and an'explosion may occur.

. g The present invention will. be apparent. tothose "skilled I of transformers 44 and 45.

directly connected to the power line conductors 40 and r the fuel burner unit to be controlled. The apparatus 16 may then be reset to the normal condition, that is the condition shown in the single figure, by manually pressing on the reset button 20.

The over all control of the apparatus shown in the single figure is achieved by a means responsive to the need for operation of the fuel burner unit being controlled. In the modification shown, this means is a thermostat 21. It is recognized however that the means 21 may for example be a manual stop-start station.

The second basic portion of the system disclosed in the single figure is the electronic flame detector, desig nated 22. This electronic flame detector includes a hot cathode-electron discharge device 23, having an anode 24 a control electrode 25, an indirectly heated cathode 26 and a cathode heater or filament 27. The electronic flame detector 22 is controlled by a photocell 28 which is positioned to View the flame at the fuel burner unit being controlled. The output of the electronic flame detector 22 is a flame relay 29 having a winding 30 and switches 31, 32, and 33. As will be shown, electronic flame detector 22 is of the type which energizesrelay 29' in the absence of flame at the fuel burner unit and there'- fore relay 29 is shown in an energized condition wherein switches 31 and 32 are closedand switch 33 is open.

The third basic portion of the system disclosed in the single figure is the fuel burner unit which is being con} trolled by means of the reference numeral 34. The fuel burner unit includes a main burner 35, a pilot burner 36, a main burner'valve 37, a pilot burner valve 38, and ignition means in the form of an ignition transformer 39. The basic over all operation of the system disclosed is such that the control network 10 responds to a signal indicating the need for operation of the fuel burner unit 34 to energize the fuel burner unit under the control of the electronic flame detector 22 which monitors the presence or absence of flame at the fuel burner unit 34. Energizing voltage is derived from an AC. source, not shown, which is connected to the power line conductors 40 and 41. The power line conductors 40 and, 41 are connected to the primary windings 42 and 43 respectively The primary winding 43 is 41, whereas the primary winding 42 is connected through a limit control 46, thus providing an additional safety feature. which insures that upon limit operation, the electronic flame detector. is not de-energized whereas the control network 10 is de-energized, I Transformer ha a tapped secondary winding 47,

Patented Oct. 11, 1969 a This secondary winding 47 provides voltage for the operation of the control network 10.

Transformer 45 is provided with a secondary 48 and a. secondary winding 49. Secondary winding 48 is a high voltage winding and provides operating voltage for the discharge device 23 and the photocell 28. Secondary winding 49 provides operating voltage for the cathode heater 27 of discharge device 23. As will be explained, secondary winding 49 is in the initial energizing circuit for the heater 27 whereas the heater 27 is maintained energized through a circuit which includes the secondary winding 47 of transformer 44.

Considering now the operation of the control apparatus in detail, the apparatus as shown in the single figure is shown in the standby condition wherein the main burner control relay 11 is de-energized and the flame relay 29 is energized.

. The electron discharge device 23 has its control electrode 25 connected to the cathode through a resistor 50 which is shunted by a capacitor 51. Photocell 28 does not view a flame at the fuel burner unit 34 and therefore control electrode 25 is at substantially the same potential as cathode 26 and the discharge device 23 is in a conducting condition, to maintain flame relay 29 energized. In this standby condition, the cathode heater 27 is energized through the initial energizing circuit which can be traced from the upper terminal of secondary winding 49 through conductor 52, heater 27, conductor 53, switch 14, and conductor 54 to the lower terminal of the secondary winding 49.

Assume now that there is a need for operation of the fuel burner unit 34, which is indicated by thermostat 21 closing its switch. This completes an initial energizing circuit for the winding 12 of the main burner control relay 11. This circuit can be traced from the tap on secondary winding 47 through conductor 55, heater 18, conductor 56, switch 31, conductor 57, winding 12, thermostat 21, conductor 58, switch 17, and conductor 59 to the lower terminal of secondary winding 47. From this above traced circuit, it can be seen that the main burner control relay 11 is energized only when the safety switch is in a closed condition, when the safety switch heater has electrical continuity, and when the switch 31 controlled by flame relay 29 is in a closed condition, thereby indicating that the electronic flame detector 22 is in a condition indicating the absence of flame at the fuel burner unit 34. If a component failure has occurred in the flame detector 32, for example a failure which renders discharge device 23 non-conductive such as the opening of the heater circuit, flame relay 29 is deenergized and switch 31 is open so that the apparatus will not respond to the call for operation of the fuel burner unit by the thermostat 21.

However, as assumed, the electronic flame detector 22 is operative at this time and therefore the main burner control relay 11 is energized. Energization of this relay causes the switches 13 and 15 to close and the switch 14 to open. The opening of the switch 14 opens the initial energizing circuit for the heater 27 of the discharge device 23 and the closing of switch 13 completes a further circuit which energizes this heater. Furthermore, the closing of switch 13 completes a circuit which will subsequently be effected to maintain or provide a running energizing circuit for control relay 11 and heater 27.

Considering now the further circuit for the heater 27, this circuit can be traced from the upper terminal of secondary winding 47 through conductors 60 and 52, heater 27, conductor 53, switch 13, conductors 61 and 57, switch 31, conductor 56, heater 18, and conductor 55 to the tap of secondary winding 47.

This above traced circuit maintains the heater 27 of discharge device 23 energized untilv such time as the electronic flame detector 22 responds to the presence .of flame at the fuel burner unit. Energization of'tlie'main control relay 11 also causes the switch 15 to be closed and this completes a circuit energizing portion of the fuel burner unit 34. Specifically the pilot valve 38 and the ignition means 39 are energized, the ignition means being energized through the closed switch 32 of the flame relay 29. Therefore, flame is normally established at the pilot burner 36 and is detected by photocell 28.

Photocell 28 is a rectifying type photocell in which the anode is identified by the reference numeral 62 and the cathode is identified by the reference numeral 63. The cathode 63 is connected to thelower terminal of secondary winding 48 and the anode 62 is connected through a capacitor 64 to the upper terminal of this secondary winding. Therefore, capacitor 64 is charged to the polarity shown in the single figure when photocell 28 detects flame at the fuel burner unit. This charge on capacitor 64 is then distributed through a network including a resistor 65 and the parallel connected resistor 50 and capacitor 51 to charge the capacitor 51 ina direction to cause the control electrode 25 of discharge device 23 to become negative with respect to its cathode 26. This then renders discharge device 23 non-conductive and the flame relay is thereby de-energized.

The de-energization of flame relay 29 causes switches 31 and 32 to open and switch 33 to close. The opening of switch 31 de-energizes the heater 18 of the safety cutout device 16 and also breaks the initial energizing circuit for the winding 12 of the main burner control relay 11. However, the burner control relay 11, as well as the cathode heater 27 are maintained energized through a running energizing circuit which can be traced from the upper terminal of secondary winding 47 through conductors 60 and 52, heater 27, conductor 53, switch 13, conductor 61, winding 12, thermostat 21, conductor 58, switch 17, and conductor 59 to the lower terminal of secondary winding 44.

It can be seen from this above traced circuit that in order for the main control relay 11 to be maintained energized it is necessary that electrical continuity exist in the heater circuit for heater 27 as well as in the heater itself. Since the switch 15 controlled by the main control relay 11 is in over-all control of'the fuel burner unit 34, it will be appreciated that if at any time during the running portion of the apparatus, the electronic flame detector 22 should become inoperative due to opening of the heater circuit for heater 27, relay 11 is immediately de-energized and all components of the fuel burner unit 34 are likewise de-energized. This safety feature is especially desirable in the case of an electronic flame detector such as detector 22, in which the presence of flame causes the flame relay 29 to be de-energized by virtue of the discharge device 23 becoming non-conductive. The open circuiting of the filament heater therefore causes a simulated presence of flame and during the running condition such a failure is not detected. If a flame failure should then occur, the flame relay 29 remains de-energized and raw fuel is admitted to the area of the fuel burner, possibly resulting in an explosion.

Considering once again the de-energization of the flame relay 29, the closing of switch 33 completes an energizing circuit for the main burner valve 37 and this valve is then energized to admit fuel to the main fuel burner 35. This fuel is ignited by the pilot burner 36 and the apparatus is then in the running condition wherein the main control relay 11 is energized, the flame relay 29 is de-energized, and the actuator 18 of the safety cutout device 16 is de-energized.

From the above description, it can be seen that I have provided an improved control apparatus wherein the main burner control relay 11 is maintained energized through a running circuit which insures that the electronic flame detector is in an operating condition. Specifically, a running circuit is provided for relay 11 which includes the cathode heater 27 of discharge device 23 such that'a failure of this cathode heater causes de-enerswitch and a normally closed switch, an electronic flame detector including an electron discharge device having an electrically energizable cathode heater, a flame relay connected in circuit with said electron discharge device and including a switch which is moved to a closed position'upon said electronic flame detector detecting the absence of flame at the fuel burner unit, initial energizing circuit means for said cathode heater including said normally closed switch of said main burner control relay such that said electronic flame detector is initially rendered operative only upon said burner control relay being in a de-energized condition, initial energizing circuit means for said main burner control relay including said flame relay switch and including means responsive to the need for operation of the fuel burner unit such that said main burner control relay is energized upon such a need and upon said electronic flame detector detecting the absence of flame at the fuel burner unit, and running circuit means for said main burner control relay and said cathode heater and controlled by said normally open switch of said main burner control relay such that said main burner control relay is maintained energized upon a call for operation of the fuel burner unit and only upon the cathode heater of said electron discharge device maintaining electrical continuity.

2. Burner control apparatus for use with a fuel burner unit, comprising; a main burner control relay including switch means adapted to be connectedto the fuel burner unit such that the fuel burner unit is energized upon ener-' gization of said main burner control relay, an electronic flame detector including means to sense the presence of flame in the fuel burner unit and including a hot cathode discharge device controlled thereby such that said electron discharge device is rendered non-conductive in the presence of flame in the fuel burner unit, a flame relay connected in circuit with said electron discharge device to be de-energized in the presence of flame at the fuel burner unit, initial energizing circuit means for said main burner control relay controlled by switch means of said flame relay which are closed when said flame relay is energized, such that said main burnercontrol relay may be energized only in the absence offlame at the fuel burner unit, and running energizing circuit means for said m-ain burner control relay including switch means controlled by said main'burner control relay and including electrically energizing means for the cathode of said electron discharge device such that said main burner control relay is maintained energized so long as said energizing means for the cathode of said electron discharge device has electrical continuity.

3. Burner control apparatus comprising; a main burner control relay including switch means, first circuit means controlled by said main burner control relay switch means arranged to operatively energize a fuel burner unit upon energization of said main burner control relay, an electronic flame detector including means responsive to the presence of flame at the fuel burner unit connected in controlling relation to an electron discharge device to render said discharge device conductive upon the absence of flame at the fuel burner unit, said electron discharge device being a hot cathode type device including an electrically energizable cathode heater, a flame relay connected in circuit with said electron discharge device, energizing circuit means for the cathode heater of said discharge dew'ce controlled by switch means of said main burner control relay toinitially energize said heater upon said main burner control relay being in a de-energized condition, initial energizing circuit means for said,

main burner control relay including switch means of said flame relay which are closed when said flame relay is energized, and a running energizing circuit for said main burner control relay and said heater, said running circuit including and being controlled by switch means of said main burner control relay which are closed when said main burner control relay is energized to thereby insure that said main burner control relay is de-energized in the event that said electronic flame detector becomes inoperative to sense the absence of flame at the fuel burner'unit due to an open circuit in the cathode heater thereof.

4. Burner control apparatus for use with a fuel burner unit, comprising; an electronic flame detector having means arranged to sense the presence or absence of flame at the fuel burner unit and connected in controlling relation to an electron discharge device, said electron device being of the hot cathode type having an electrically energizable cathode heater and being rendered conductive in the absence of flame at the fuel burner unit, a flame relay having a winding and a switch which is open when said relay is de-energized, circuit means connecting said flame relay winding in circuit with said electron discharge device to thereby energize said flame relay winding upon said flame sensing meanssensing the absence of flame at the fuel burner unit; safety cutout means having a time delayed electrically energizable actuator and having a normally closed switch connected in controlling relation to the fuel burner unit, a main burner control relay having a winding and first and second switches which are open when said winding is de-energized and a third switch which is closed when said winding is de-energized; initial energizing circuit means for the cathode heater of said electron discharge device controlled by said third switch of said main burnercontrol relay such that said electron discharge device is initially heated to an operating temperature when said main burner control relay is in a deenergized position, an initial energizing circuit for the winding of said main burner control relay including means. responsive to the need for operationof the fuel burner unit and also including said switch of said flame relay and the actuator of said safety lock-out means, such that the winding of said main burner control relay is energized initially only when said flame relay is in a condition indicating the absence of flame at the fuel burner unit and when safety cutout means actuator has electrical continuity, a running energizing circuit for the winding of said main burner control relay and the cathode heater of said electron discharge device, said running circuit including and being controlled by the second switch of said main burner control relay, and further means controlled by the first switch of the main burner control relay adapted to be connected to the fuel burner unit to energize the same upon a need for operation of the fuel burner unit, to thereby normally establish a flame at the fuel burner unit, which flame is sensed by said electronic flame detector to cause de-energization of said flame relay and maintain said main burner control relay energized through said running energizing circuit, and to subsequently de-energize said main burner control relay winding in the event that said electronic flame detector becomes inoperative to detect the absence of the flame at the fuel burner unit due to failure of electrical continuity of its cathode heater.

5. A burner control apparatus for use with a fuel burner unit, comprising; an electronic flame detector including means arranged to sense the presence of flame at the fuel burner unit and including an electron discharge device having an electrically energizable cathode heater, a burner control relay including switch means arranged to be connected to energize the fuel burner unit to produce a flame at the fuel burner unit, a starting energizing circuit for said burner control relay including normally closed switch means controlled by said electronic flame detector and arranged to initially energize said burner control relay only upon said electronic flame detector indicating the; absence of flame in the fuel burner unit, said starting circuit being opened by said flame detector switch means upon said flame detector indicating the presence of flame at the fuel burner unit, and a running circuit for said burner control relay including said cathode heater so that a' failure of said electron discharge device due to open c'ircuiting' of said cathode heater is effective to de-energize said burner control relay and thereby prevent energization of the fuel burner unit with said electronic flame detector in an inoperative condition, said running circuit including and being controlled by switch means of said burner control relay arranged to render said running circuit effective upon energization of said burner control relay.

6. In a burner control system having a burner control relay which when energized controls a fuel burner unit to establish flame thereat, in which the continued energization of the burner control relay is dependent upon the tie-energization of a flame relay to indicate a proper flame condition, and having an electronic flame detector of the type having ahot cathode discharge device including an electrically energizable cathode heater, which discharge device controls the energization of the flame relay, the improvement comprising; an energizing circuit for said burner control relay including the cathode heater of said discharge device such that said burner control relay is de energized to thereby de-energize the fuel burner unit uponfailure of said electronic flame detector due to open circuit of said cathode heater.

7. Burner control apparatus for use with a fuel burner unit comprising; a burner control relay including switch means adapted to be connected to the fuel burner unit to control energization thereof, an electronic flame detector including means arranged to sense the presence of flame at the fuel burner unit and including a hot cathode electron discharge device having an electrically energizable cathode heater therefor, an initial energizing circuit for said burner control relay including means responsive to need for operation of the fuel burner unit, a running energizing circuit for said burner control relay including in circuit therewith the cathode heater of said electron discharge device to' thereby maintain said burner control relay energized so long as there is a need for operation of the fuel burner unit and so long as the cathode heater of 'said electron' discharge device'has electrical continuity, means effective to open said initial energizing circuit after energization of said burner control relay, and further means effective to complete said running energizing circuit after energization of said burner control relay.

8 A burner control apparatus for use with a fuel burner unit, comprising; a burner control relay including switch means adapted to be connected to the fuel burner unit, an electronic flame detector including a flame relay and a hot cathode discharge device including an elec-' trically energizable heater, a safety cutoff device including a switch connected in controlling relation to the burner control relay and including an electrically energizable actuator, initial energizing circuit means for said burner control relay including said safety cutoff device actuator and switch means of said flame relay which are closed when said flame relay is in a position indicating the absence of flame in the fuel burner unit, said flame relay switch means being effective to open said initial energizing circuit means when said flame relay is in a position indicating the presence of flame in the fuel burner unit, and running energizingcircuit means for said burner control relay which is effective upon said flame relay assuming a position indicating the presence of flame, said running energizing circuit means including the heater of said discharge device such that said burner control relay is de-energized in the event that said electron discharge device fails due to an open heater circuit.

9. In a burner control system having a burner control relay with a winding which is energized in response to the need for operation of a fuel burner unit to establish flame thereat and whose continued energization is dependent ,upon a flame relay being in a condition to indicate the presence of flame at the fuel burner unit, the system having an electronic flame detector including a flame relay controlled by a hot cathode electron discharge device which is controlled in accordance with the presence of flame at the fuel burner unit and is rendered non-conductive when flame is present in the fuel burner unit, the improvement comprising; an energizing circuit for said burner control relay winding included in series circuit therewith a cathode heater of said electron discharge de vice such that said burner control relay winding is deenergized in the event that said electronic flame detector becomes inoperative to sense the absence of flame at the fuel burner unit due to failure of electrical continuity of said cathode heater.

References Cited in the file of this patent UN lTED STATES- PATENTS Lange Sept. 16, 1952 

